1. Field of the Invention
The present invention relates to an optical disk apparatus used for performing data-processing with optical disks. The data-processing may include recording, reading or deleting of data. The optical disk may include a magneto-optical disk with which magnetic field modulation or optical pulse modulation may be used for performing required data-processing.
2. Description of the Related Art
FIGS. 36 and 37 of the accompanying drawings show a conventional disk apparatus disclosed in JP-A-11(1999)-213419. As illustrated, the conventional apparatus includes an elongated swing arm 90, a flexible suspension 91, a fine adjustment actuator 92, a mirror 93 and a slider 94. The suspension 91 is attached, at one end, to the swing arm 90, while carrying, at the other end, the actuator 92, the mirror 93 and the slider 94. The swing arm 90 is attached to a spindle 95 which in turn is connected to a motor Ma. Upon turning on the motor Ma, the swing arm 90 is caused to rotate forward or backward about the axis of the spindle 95, whereby the slider 94, together with the actuator 92 and the mirror 93, is moved in the tracking direction Tg over the disk D. The fine adjustment actuator 92 is designed to make fine adjustments to the position of the mirror 93 and the slider 94 in the tracking direction Tg. As shown in FIG. 37, the slider 94 carries a lens assembly consisting of two objectives 96.
Further, the conventional apparatus includes a spindle motor Mb arranged below the disk D. In operation, the disk D is rotated at high speed by the motor Mb. The rotation of the disk D causes air to be drawn between the slider 94 and the disk D, whereby the slider 94 floats above the disk D due to the air introduced between the slider 94 and the disk D.
The conventional disk apparatus also includes a light source 97 to emit a laser beam and a mirror 98 disposed in the path of the laser beam. As shown in FIG. 36, the laser beam is reflected on the mirror 98, to travel toward the other mirror 93. The laser beam is reflected on the mirror 93, to be directed downward and enter the objectives 96. The objectives 96 focus the laser beam and form a beam spot on the recording layer of the disk D.
The seeking operation of a desired one of the tracks of the disk D is performed while the swing arm 90 is being caused to pivot on the spindle 95. Once the required track is found, the beam spot may need to remain on the target track for a while. For this purpose, tracking control is carried out by driving the fine actuator 92 for finely adjusting the position of the mirror 93 and the slider 94 in the tracking direction Tg, so that the mirror 93 and the slider 94 can follow the deviation of the target track.
Though provided with the fine actuator designed to move the relevant components in the tracking direction Tg, the conventional optical disk apparatus has been found disadvantageous in the following points.
When the disk D is rotated at high speed, the disk surface may fluctuate in the focusing direction shown by an arrow Fs in FIG. 37. The fluctuation may be caused by unstable rotation of the disk spindle, initial geometrical error of the disk D or warping of the disk D due to gravity.
When such fluctuation occurs in the disk D, the slider 94 will rise and fall to maintain the prescribed constant distance between the disk surface and the slider 94. Hence, the mirror 93, mounted on the slider 94, also moves up and down. On the other hand, the level of the laser beam traveling toward the mirror 93 does not change. This means that the height of the laser beam relative to the mirror 93 is not constant during the fluctuation of the disk D.
Specifically, it is assumed that normally (i.e., with no disk fluctuation), the center C1 of the laser beam strikes upon apoint n1 of the mirror 93, as shown in FIG. 37. However, when the disk D moves downward, as shown in FIG. 38, the center of the laser beam (C2) strikes upon a higher point n2 on the mirror 93. As a result, the light path extending from the mirror 93 to the objectives 96 will shift toward the spindle 95 (see arrow Na). Likewise, when the disk D moves upward, the light path will shift in the opposite direction or away from the spindle 95.
When such shifting of the light path occurs, the center of the laser beam will deviate from the optical axis of the objectives 96, which may make it difficult or even impossible to properly form an appropriately small beam spot on the recording layer of the disk D. In particular, when a small, solid immersion lens is used for the lower objective 96a of the lens assembly, the laser beam may utterly miss the lower lens 96a. It should be noted here that the fine actuator 92 cannot help to solve the problems, since the actuator 92 moves the mirror 93 and the slider 94 only in the tracking direction Tg (FIG. 36), which is perpendicular to the shifting direction Na of the light path.
The present invention has been proposed under the circumstances described above, and its object is to overcome the conventional problems stemming from the fluctuation of an optical disk, so that data-recording operation or data-reading operation with an optical disk is properly performed.
According to a first aspect of the present invention, there is provided an optical disk apparatus which includes: a light source for emitting a laser beam; an objective for focusing the laser beam; a slider holding the objective and arranged to float relative to an optical disk; a suspension for supporting the slider; a first mirror supported by the suspension and spaced from the slider in a focusing direction, the first mirror being arranged to reflect the laser beam traveling in a first direction which is non-parallel to the focusing direction, so that the reflected laser beam enters the objective; and a seek mechanism for moving the suspension so that the first mirror and the slider are moved in a tracking direction. The first mirror is rotatable about a first axis for causing the reflected laser beam to shift in the first direction.
Preferably, the first mirror may be rotatable about a second axis which is non-parallel to the first axis for causing the reflected laser beam to shift in a second direction which is non-parallel to the first direction.
Preferably, the apparatus of the present invention may further include a second mirror for reflecting the laser beam between the light source and the first mirror. The second mirror may be rotatable about a third axis for causing the reflected laser beam to shift in a third direction which is non-parallel to the first direction.
According to a second aspect of the present invention, there is provided an optical disk apparatus which includes: a light source for emitting a laser beam; an objective for focusing the laser beam; a slider holding the objective and arranged to float relative to an optical disk; a suspension for supporting the slider; a first mirror supported by the suspension and spaced from the slider in a focusing direction, the first mirror being arranged to reflect the laser beam traveling in a first direction which is non-parallel to the focusing direction, so that the reflected laser beam enters the objective; a seek mechanism for moving the suspension so that the first mirror and the slider are moved in a tracking direction; and a second mirror disposed between the light source and the first mirror for reflecting the laser beam emitted by the light source toward the first mirror. The second mirror is rotatable about a first axis for causing the reflected laser beam to shift in the focusing direction.
Preferably, the second mirror may be rotatable about a second axis for causing the reflected laser beam to shift in a second direction which is non-parallel to the first direction.
In a preferred embodiment of the present invention, the first mirror may be rotatable about a third axis for causing the reflected laser beam to shift in a third direction which is non-parallel to the first direction.
Preferably, the seek mechanism may include a swing arm for moving the suspension in the tracking direction. The first direction may be non-parallel to the tracking direction.
The above apparatus may further include a detector for receiving the laser beam which is reflected on the disk and returned along a return path. The detector is designed to generate a tracking error detection signal when the return path deviates in a tracking error direction. The detector is designed to generate a beam shift detection signal when the return path deviates in a beam shift direction.
Preferably, the detector may be provided with a photoelectric device and an arithmetical unit. The photoelectric device may include at least first to fourth light-receiving elements, wherein the first and the second light-receiving elements are spaced from the third and the fourth light-receiving elements in the beam shift detection. In addition, the first and the third light-receiving elements may be spaced from the second and the fourth light-receiving elements in the tracking error direction. The arithmetical unit may be arranged to generate the tracking error detection signal based on a difference between a sum of signals from the first and the third light-receiving elements and a sum of signals from the second and the fourth light-receiving elements. In addition, the arithmetical unit is arranged to generate the beam shift detection signal based on a difference between a sum of signals from the first and the second light-receiving elements and a sum of signals from the third and the fourth light-receiving elements.
In a preferred embodiment of the present invention, the seek mechanism may cause the suspension to be moved linearly in the tracking direction. The first direction may coincide with the tracking direction.
In a preferred embodiment of the present invention, the apparatus may include a photoelectric device supported by the suspension, wherein the photoelectric device is formed with a through-hole for allowing passage of the laser beam. The photoelectric device is designed to detect deviation of the laser beam relative to the through-hole in the focusing direction.
In the above case, the photoelectric device may be provided with at least two light-receiving elements spaced from each other in the focusing direction, wherein the through-hole may intervene between the two light-receiving elements.
In addition, the above apparatus may further include an arithmetical unit designed to generate a beam shift detection signal based on a difference between signals supplied from the light-receiving elements.
According to a third aspect of the present invention, there is provided an optical disk apparatus which includes: a light source for emitting a laser beam; an objective for focusing the laser beam; a slider holding the objective and arranged to float relative to an optical disk; a suspension for supporting the slider; a mirror supported by the suspension and spaced from the slider in a focusing direction, the mirror being arranged to reflect the laser beam traveling in a first direction which is non-parallel to the focusing direction, so that the reflected laser beam enters the objective; a seek mechanism for moving the suspension so that the mirror and the slider are moved in a tracking direction; and position adjusting means for finely moving the slider and the mirror in the first direction.
In the above apparatus, the seek mechanism may include a carriage to which the suspension is connected, a carriage guide elongated in the tracking direction and a voice coil motor for driving the carriage along the carriage guide.
Preferably, the carriage may include a casing supported by the carriage guide and a supporting plate to which the suspension is connected. The supporting plate is movable relative to the casing and connected to the voice coil motor.
The apparatus of the present invention may further include a mirror holder supported by the suspension, and a gimbal spring arranged between the mirror holder and the slider so that the slider is pivotable on the mirror holder.
In a preferred embodiment of the present invention, the suspension may include two flexible plates held in parallel to each other.
According to a fourth aspect of the present invention, there is provided an optical disk apparatus which includes: a light source for emitting a laser beam; an objective for focusing the laser beam; a slider holding the objective and arranged to float relative to an optical disk; a suspension for supporting the slider; a mirror supported by the suspension and spaced from the slider in a focusing direction, the mirror being arranged to reflect the laser beam traveling in a first direction which is non-parallel to the focusing direction, so that the reflected laser beam enters the objective; a seek mechanism for moving the suspension so that the mirror and the slider are moved in a tracking direction; a mirror holder supported by the suspension for holding the mirror; and a gimbal spring disposed between the mirror holder and the slider for allowing the slider to pivot on the mirror holder.
According to a fifth aspect of the present invention, there is provided a galvano-mirror which includes: a mirror plate provided with a light reflector; a supporting member for supporting the mirror plate; a torsion bar for connecting the mirror plate to the supporting member in a cantilever manner, the torsion bar being twistable about a first axis; first actuating means for rotating the mirror plate about the first axis of the torsion bar; and second actuating means for rotating the mirror plate about a second axis which is non-parallel to the first axis.
Other features and advantages of the present invention will become apparent from the detailed description given below with reference to the accompanying drawings.